1. Field of the Invention
The present invention relates to control of compression ignition engines with electronic control modules programmable to detect engine overspeed operation, and inhibiting throttle response to throttle activation after detecting overspeed engine operation.
2. Background Art
A vehicle engine may be severely damaged when the engine is driven to an overspeed condition. Of course, the upper limit of the damaging overspeed condition may be different for a variety of engines, and often depends on the number of cylinders, or/and stroke of the cylinders, and other structural parameters of the vehicle engine. Typically engine brakes can be enabled to prevent an engine overspeed condition. Engine compression brake logic prohibits enabling the engine compression brakes whenever the engine is fueling. This is necessary to prevent possible engine or engine compression brake damage. Therefore, an engine overspeed condition may occur if throttle actuation is continued by an operator even though an engine overspeed threshold has already been reached by the engine.
Overspeed control may be particularly important where travel over different terrain may complicate operation of the vehicle. In particular, if an operator is driving a truck up hill, typically the throttle is being actuated to keep engine speeds and torque at a high level. After cresting the top of the hill, if the operator keeps his foot on the accelerator pedal, engine compression brakes will not enable, since the electronic engine controller inhibits engine brake activation while fueling the engine. Such a controller normally has been programmed into the controller since there are very few times that the operator would want to enable the engine brakes when the driver is requesting more power from the engine. However, after cresting on the top of the hill, the vehicle begins a downward descent and speed control would be desirable. Nevertheless, if the operator keeps his foot on the accelerator pedal, the vehicle will be unable to take advantage of engine braking, the normal resistence to displacement of the pistons in the cylinders, when the fueling level is inadequate to maintain the speed at which the engine is turning.